The present invention relates to a device for maintaining the oscillation of a balance for a timepiece, comprising a balance having two magnets attached thereto, two complementary transistors constituting an astable multivibrator, and a coil coupled as a load to the astable multivibrator and combining pick-up and driving functions.
Several devices of this type are already known, notably from Swiss Pat. No. 347,783, French Pat. No. 2,000,706 and British Pat. No. 1,270,037. However, in the device of the Swiss Patent it has been experienced that this device does not completely achieve its object unless it operates at a substantially constant temperature, which is not generally the case. In the device of the French Patent, the time constant of the RC circuit connected parallel to the emitter of the control transistor thereof cannot be too high, because otherwise the condenser in the RC circuit will be charged increasingly by the emitter current of the control transistor, resulting in the both the value of the emitter resistor in the RC circuit and also its protective effect being restricted. Further, the device of the British Patent is complex in structure and cannot be made into a small-size, so that it is unsuitable for industrial mass production.
The present invention obviates the foregoing disadvantages of the known devices of this type and provide a new, improved device for maintaining the oscillation of a balance for a timepiece.